1. Field of the Invention
The present invention relates to an image reading apparatus and an image forming apparatus using the image reading apparatus.
Priority is claimed on Japanese Patent Application No. 2010-080723, filed Mar. 31, 2010, the contents of which are incorporated herein by reference.
2. Description of Related Art
An image forming apparatus in conventional such as copiers, printers, fax machines, or multifunction printers which are provided with a plurality of the functions of these apparatuses is provided with an image reading apparatus. The image reading apparatus is provided at an upper portion of the main unit of the image forming apparatus. The image reading apparatus is configured so as to irradiate light onto an image of an original document and read the original document image as image data, by receiving reflected light therefrom. In addition, the image reading apparatus includes: a light source unit that irradiates light onto an original document; and an image sensor that receives feedback light from the original document and converts it into image data, and the like.
Namely, the image reading apparatus includes: a light source that made of a lamp such as an LED or a xenon lamp for irradiating light onto a surface of an original document placed on a glass surface for an original document; a group of mirrors that sequentially reflect the light that has been reflected from the original document to guide it to an image forming lens (a condenser lens); and an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) that converts the light condensed by the image forming lens into electric signals.
The image forming lens and the image sensor such as a CCD of the image forming apparatus are mounted on a bottom surface of a chassis that is provided in the main unit of the image reading apparatus. When the image forming lens and the image sensor are mounted and fixed on the bottom surface of the chassis, a light acceptance portion of the image sensor is adjusted so as to be vertical to an optical axis of the image forming lens. In addition, the positions of the image forming lens and the image sensor are adjusted in the optical axis direction so that the focus and magnification are at the optimum. The image forming lens and the image sensor that the positions are adjusted in this manner are fixed with screws or by use of an adhesive.
Incidentally, in the aforementioned conventional image reading apparatus, fixation with an adhesive is more preferable than fixation with screws for the fixation of the image forming lens and the image sensor after their positional adjustment. Fixation with screws is likely to cause a displacement at the time of final tightening. Therefore, fixation with an adhesive is advantageously simpler.
However, in the case of fixation with an adhesive, the positions of the image forming lens and the image sensor are displaced due to a volume change (contraction) of the adhesive that occurs in the process in which the adhesive cures. This results in a disadvantage in that it is not possible to obtain a predetermined image quality.